Micro-electro-mechanical device and manufacturing method for the same

ABSTRACT

It is an object of the present invention to provide a micro-electro-mechanical-device having a microstructure and a semiconductor element over one surface. In particular, it is an object of the present invention to provide a method for simplifying the process of forming the microstructure and the semiconductor element over one surface. A space in which the microstructure is moved, that is, a movable space for the microstructure is formed by processing an insulating layer which is formed in a process of forming the semiconductor element. The movable space can be formed by forming the insulating layer having a plurality of openings and making the openings face each other to be overlapped each other.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/469,125, filed Aug. 31, 2006, now allowed, which claims the benefitof a foreign priority application filed in Japan as Serial No.2005-258072 on Sep. 6, 2005, both of which are incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a micro-electro-mechanical device whichhas a microstructure and a semiconductor element, and a manufacturingmethod therefor.

2. Description of the Related Art

In recent years, a micro mechanical system called MEMS is activelyresearched. MEMS is an abbreviated name of a micro-electro-mechanicalsystem, which is sometimes simply called a micromachine. A micromachinein general corresponds to a minute device in which “a movablemicrostructure having a three-dimensional structure” is integrated usinga semiconductor minute processing technique. The microstructure has athree-dimensional structure, a movable portion, and a space for moving.

A micromachine can control its microstructure by using an electroniccircuit. Therefore, it is said that an autonomous decentralized typesystem can be formed which performs a series of operations by processinginformation obtained by a sensor in an electronic circuit and executingthe operation through an actuator or the like, instead of a centralprocessing control type system such as a conventional device using acomputer.

Many strudies have been made on a micromachine. For example, an advancedMEMS wafer level package is proposed to overcome a problem that amanufacturing process cannot be used with equipment for wafermanufacturing and plastic assembly (Patent Document 1).

In addition, a method of manufacturing a semiconductor package isproposed in which a microstructure and a semiconductor element areseparately formed over countering substrates and are electricallyconnected to each other (Patent Document 2).

In addition, there is a document of a thin-film-shaped and crystallizedmechanical device and an electro-mechanical device called MEMS (PatentDocument 3). In the Patent Document 3, an amorphous material, ananocrystalline material, a microcrystalline material, and apolycrystalline material are listed as a starting material of a thinfilm. As the material thereof, silicon, germanium, silicon germanium, ananisotropic dielectric material, an anisotropic piezoelectric material,copper, aluminum, tantalum, and titanium are listed. In addition, it isdescribed that a thin-film-shaped amorphous silicon layer is formed overa glass substrate, then, crystallized. In the crystallization, laserirradiation is controlled so that in an inner part, a crystallineproperty which can provide favorable mechanical characteristics isrealized.

-   [Patent Document 1] Japanese Patent Application Laid-Open No.    2001-144117-   [Patent Document 2] Japanese Patent Application Laid-Open No.    2003-297876-   [Patent Document 3] Japanese Patent Application Laid-Open No.    2004-1201

As described in Patent Document 1, a microstructure in a micromachine isformed by a process using a silicon wafer. In particular, in order toobtain a material with sufficient thickness and strength to manufacturea microstructure, most micromachines in practical use are manufacturedusing silicon wafers.

In addition, in accordance with a mass productivity of a micromachinehaving a minute structure, reduction in manufacturing cost is desired.Therefore, a method in which a microstructure and a semiconductorelement controlling the microstructure are integrated is desired.However, when integrating a microstructure and a semiconductor element,the manufacturing process becomes complicated since the manufacturingprocess of the microstructure and that of the semiconductor element aredifferent, e.g., etching of a sacrificial layer. Since the processes aredifferent, when integrating the microstructure and the semiconductorelement, there is a possibility that the microstructure or thesemiconductor element is damaged and does not operate. Therefore, mostmicromachines in practical use have microstructures and semiconductorelements manufactured in different processes.

SUMMARY OF THE INVENTION

In view of the foregoing, it is an object of the present invention toprovide a micromachine (hereinafter referred to as amicro-electro-mechanical-device) having a microstructure and asemiconductor element over one surface. In particular, it is an objectof the present invention to provide a method for simplifying the processof forming a microstructure and a semiconductor element over onesurface.

In view of the foregoing problems, in the present invention, a space inwhich a microstructure is moved, that is, a movable space for themicrostructure is formed by processing an insulating layer which isformed in a process of forming a semiconductor element. The movablespace can be formed by forming an insulating layer having a plurality ofopenings and making the openings face each other to be overlapped eachother.

In particular, in order to solve the foregoing problems, the presentinvention provides the following methods.

One example of the present invention is a manufacturing method of amicro-electro-mechanical device which includes, forming a peeling layer,forming a first structure layer in a first region over the peelinglayer, forming a first insulating layer covering the first structurelayer, forming a first opening in the first insulating layer in thefirst region so that the first structure layer is exposed, forming asecond structure layer in a second region, forming a second insulatinglayer covering the first opening and the second structure layer, formingsecond openings in the second insulating layer so that the firststructure layer and the second structure layer are exposed, removing thepeeling layer, and forming a space between the first structure layer andthe second structure layer by making the second openings face each otherto be overlapped each other. That is, the second openings are formed inthe second insulating layer both in the first region and the secondregion.

One example of the present invention is a manufacturing method of amicro-electro-mechanical device which includes, forming a peeling layer,forming a first structure layer in a first region over the peelinglayer, forming a first insulating layer covering the first structurelayer, forming a first opening in the first insulating layer in thefirst region so that the first structure layer is exposed, forming asecond structure layer in a second region, forming a second insulatinglayer which contains an organic material to cover the first opening andthe second structure layer, forming second openings in the secondinsulating layer so that the first structure layer and the secondstructure layer are exposed, removing the peeling layer, and forming aspace between the first structure layer and the second structure layerby making the second openings face each other to be overlapped eachother.

One example of the present invention is a manufacturing method of amicro-electro-mechanical device which includes, forming a peeling layer,forming a first structure layer and a semiconductor layer in a firstregion and a second region over the peeling layer, respectively, forminga first insulating layer covering the first structure layer and thesemiconductor layer, forming a first opening in the first insulatinglayer in the first region so that the first structure in the firstregion is exposed, and a second opening in the first insulating layer inthe second region, forming a conductive layer and a second structurelayer so as to fill the second opening, forming a second insulatinglayer covering the first opening, the conductive layer, and the secondstructure layer, forming third openings in the second insulating layerin the first region and the second region so that the first structurelayer and the second structure layer are exposed, removing the peelinglayer, and forming a space between the first structure layer and thesecond structure layer by making the third openings face each other tobe overlapped each other.

One example of the present invention is a manufacturing method of amicro-electro-mechanical device which includes, forming a peeling layer,forming a first structure layer and a semiconductor layer in a firstregion and a second region over the peeling layer, respectively, forminga first insulating layer covering the first structure layer and thesemiconductor layer, forming a first opening in the first insulatinglayer in the first region so that the first structure in the firstregion is exposed, and a second opening in the first insulating layer inthe second region, forming a conductive layer and a second structurelayer so as to fill the second opening, forming a second insulatinglayer which contains an organic material to cover the first opening, theconductive layer, and the second structure layer, forming third openingsin the second insulating layer in the first region and the second regionso that the first structure layer and the second structure layer areexposed, removing the peeling layer forming a space between the firststructure layer and the second structure layer by making the thirdopenings face each other to be overlapped each other. That is, the thirdopenings are formed in the second insulating layer both in the firstregion and the second region so as to expose the first structure layerand the second structure layer, respectively.

One example of the present invention is a manufacturing method of amicro-electro-mechanical device which includes, forming a peeling layerover a first substrate, forming a first structure layer and asemiconductor layer in a first region and a second region over thepeeling layer, respectively, forming a first insulating layer coveringthe first structure layer and the semiconductor layer, forming a firstopening in the first insulating layer in the first region so that thefirst structure in the first region is exposed, and a second opening inthe first insulating layer in the second region, forming a conductivelayer and a second structure layer so as to fill the second opening,forming a second insulating layer covering the first opening, theconductive layer, and the second structure layer, forming third openingsin the second insulating layer in the first region and the second regionso that the first structure layer and the second structure layer areexposed, removing the peeling layer and separating the first substrate,transferring the micro-electro-mechanical device to a resin substrate (aflexible substrate), and folding the resin substrate so that a space isprovided between the first structure layer and the second structurelayer.

One example of the present invention is a manufacturing method of amicro-electro-mechanical device which includes, forming a peeling layerover a first substrate, forming a first structure layer and asemiconductor layer in a first region and a second region over thepeeling layer, respectively, forming a first insulating layer coveringthe first structure layer and the semiconductor layer, forming a firstopening in the first insulating layer in the first region so that thefirst structure in the first region is exposed, and a second opening inthe first insulating layer in the second region, forming a conductivelayer and a second structure layer so as to fill the second opening,forming a second insulating layer which contains an organic material tocover the first opening, the conductive layer, and the second structurelayer, forming third openings in the second insulating layer in thefirst region and the second region so that the first structure layer andthe second structure layer are exposed, removing the peeling layer andseparating the first substrate, transferring themicro-electro-mechanical device to a resin substrate, and folding theresin substrate so that a space is provided between the first structurelayer and the second structure layer.

One example of the present invention is a manufacturing method of amicro-electro-mechanical device which includes, forming a peeling layerover a first substrate, forming a first structure layer and asemiconductor layer in a first region and a second region over thepeeling layer, respectively, forming a first insulating layer coveringthe first structure layer and the semiconductor layer, forming a firstopening in the first insulating layer in the first region so that thefirst structure in the first region is exposed, and a second opening inthe first insulating layer in the second region, forming a conductivelayer and a second structure layer so as to fill the second opening,forming a second insulating layer so as to cover the first opening, theconductive layer, and the second structure layer, forming third openingsin the second insulating layer in the first region and the second regionso that the first structure layer and the second structure layer areexposed, removing the peeling layer and separating the first substrate,transferring the micro-electro-mechanical device to a flexible substrateprovided with a first opening portion and a second opening portion, andfolding the flexible substrate so that the first opening portion and thesecond opening portion face each other.

One example of the present invention is a manufacturing method of amicro-electro-mechanical device which includes, forming a peeling layerover a first substrate, forming a first structure layer and asemiconductor layer in a first region and a second region over thepeeling layer, respectively, forming a first insulating layer coveringthe first structure layer and the semiconductor layer, forming a firstopening in the first insulating layer in the first region so that thefirst structure in the first region is exposed, and a second opening inthe first insulating layer in the second region, forming a conductivelayer and a second structure layer so as to fill the second opening,forming a second insulating layer which contains an organic material tocover the first opening, the conductive layer, and the second structurelayer, forming third openings in the second insulating layer in thefirst region and the second region so that the first structure layer andthe second structure layer are exposed, removing the peeling layer andseparating the first substrate, transferring themicro-electro-mechanical device to a flexible substrate provided with afirst opening portion and a second opening portion, and folding theflexible substrate so that the first opening portion and the secondopening portion face each other.

In the present invention, the space may be closed by being sealed or maybe opened.

In the present invention, the first structure layer, the secondstructure layer, and the space can form a capacity.

As described above, in the present invention, the microstructure and thesemiconductor element are formed over one surface. Conventionally, aspace for moving the microstructure is formed by etching a sacrificelayer or deeply etching a silicon wafer. In the present inventionhowever, a space is formed by processing an insulating layer which isformed in a manufacturing process of a semiconductor element. Therefore,a manufacturing process can be simplified, which leads to improvement inproduction efficiency and reduction in cost, and even reduction indamage of the microstructure being manufactured can be realized.

Thus, by manufacturing the microstructure and the semiconductor elementover one surface, a micro-electro-mechanical device with simple assemblyand package, and low manufacturing cost can be provided.

In addition, in the present invention, polycrystalline silicon which iscrystallized using a metal such as nickel can be used for a structurelayer in a microstructure and an active layer of a semiconductorelement. Therefore, a micro-electro-mechanical device having amicrostructure which can resist external force and stress and asemiconductor element with favorable element characteristics over onesurface can be provided.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1E show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIGS. 2A to 2D show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIGS. 3A to 3D show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIGS. 4A to 4C show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIGS. 5A to 5C show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIG. 6 shows a manufacturing process for a micro-electro-mechanicaldevice of the present invention;

FIGS. 7A and 7B show an assembling process for amicro-electro-mechanical device of the present invention;

FIGS. 8A and 8B show an assembling process for amicro-electro-mechanical device of the present invention;

FIGS. 9A to 9E show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIGS. 10A to 10D show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIGS. 11A to 11D show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIGS. 12A to 12C show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIGS. 13A to 13C show a manufacturing process for amicro-electro-mechanical device of the present invention;

FIG. 14 shows an example of a semiconductor device of the presentinvention;

FIGS. 15A and 15B show a structure of a sensor;

FIG. 16 shows a structure of a memory cell;

FIGS. 17A and 17B show a structure of a memory cell;

FIGS. 18A and 18B show an example of a semiconductor device of thepresent invention;

FIGS. 19A and 19B show an example of a semiconductor device of thepresent invention;

FIG. 20 shows an example of a semiconductor device of the presentinvention;

FIGS. 21A and 21B show an example of a semiconductor device of thepresent invention;

FIG. 22 shows an example of a semiconductor device of the presentinvention;

FIG. 23 shows an example of a semiconductor device of the presentinvention;

FIGS. 24A and 24B show an example of a semiconductor device of thepresent invention; and

FIGS. 25A and 25B show an example of a semiconductor device of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, embodiment modes of the present invention are explainedwith reference to the drawings. However, the present invention is notlimited to the following description. As is easily understood to aperson skilled in the art, the mode and the detail of the presentinvention can be variously changed without departing from the spirit andthe scope of the present invention. Thus, the present invention is notinterpreted as being limited to the following description of theembodiment modes. Note that like portions in the different drawings aredenoted by the like reference numerals when describing a structure ofthe invention with reference to the drawings.

Embodiment Mode 1

In this embodiment mode, a method of forming a microstructure and asemiconductor element over one surface is described with reference tothe drawings. In the drawings, top views and cross-sectional views takenalong a line O-P in the top views are shown.

A microstructure and a semiconductor element of the present inventioncan be formed over one surface of a substrate having an insulatingproperty (insulating substrate). As an insulating substrate, there are aglass substrate, a quartz substrate, a plastic substrate, and the like.For example, by forming a microstructure and a semiconductor elementover a plastic substrate, a light-weight micro-electro-mechanical devicehaving high flexibility can be manufactured. In addition, by thinning aglass substrate by polishing or the like, a thinmicro-electro-mechanical device can be manufactured. Further, asubstrate obtained by forming a layer having an insulating property(insulating layer) over a conductive substrate such as metal or asemiconductor substrate such as silicon can also be used as aninsulating substrate.

First, a peeling layer 102 is formed over an insulating substrate 101(FIG. 1A). The peeling layer 102 refers to a layer which is peeledlater. As the peeling layer 102, a metal layer, a stacked-layerstructure of a metal layer and a metal oxide film, or the like may beused. The metal layer is formed of a film formed of an element selectedfrom tungsten (W), molybdenum (Mo), titanium (Ti), tantalum (Ta),niobium (Nb), nickel (Ni), cobalt (Co), zirconium (Zr), zinc (Zn),ruthenium (Ru), rhodium (Rh), palladium (Pd), osmium (Os), and iridium(Ir), or an alloy material or a compound material containing theforegoing element as its main component to have a single-layer structureor a stacked-layer structure. The peeling layer 102 can be formed bysputtering or CVD (Chemical Vapor Deposition). To form the stacked-layerstructure of a metal layer and a metal oxide film, oxide of the metalfilm can be formed on the metal film surface by performing a plasmatreatment in an oxygen atmosphere or a heating treatment in an oxygenatmosphere, after the foregoing metal layer is formed. For example, inthe case where a tungsten film formed by sputtering is formed as a metalfilm, a metal oxide film of tungsten oxide can be formed on the tungstenfilm surface by performing a plasma treatment on the tungsten film.Tungsten oxide is expressed in WO_(x), and x is 2 to 3. There are casesof x is 2 (WO₂), x is 2.5 (WO₂O₅), x is 2.75 (W₄O₁₁), x is 3 (WO₃), andthe like. When forming tungsten oxide, the values of x described aboveare not particularly limited, and the oxide to be formed may be decidedbased on an etching rate or the like. In addition, it is possible toform an oxide film on the metal layer surface by performing a plasmatreatment in the condition of high density and a low electrontemperature using high frequency (a microwave or the like) (hereinafterthe plasma in this condition is also referred to as high-densityplasma). High-density plasma has a plasma density of 1×10¹¹ cm⁻³ ormore, preferably, 1×10¹¹ cm⁻³ to 9×10¹⁵ cm⁻³ and in which high frequencysuch as a microwave (e.g., a frequency of 2.45 GHz) is used. Plasmagenerated in such a condition has a low electron temperature of 0.2 to2.0 eV. Since the high-density plasma which has a feature of lowelectron temperature has low kinetic energy of activated species, a lessdefective film with little plasma damage can be formed. Furthermore, inaddition to a metal oxide film, metal nitride or metal oxynitride may beused. In this case, a plasma treatment or heating treatment may beperformed on the metal film in a nitrogen atmosphere or an atmosphere ofnitrogen and oxygen. A condition of the plasma treatment may be setsimilarly to the foregoing one.

Next, a base layer 103 is formed over the peeling layer 102 (FIG. 1A).The base layer 103 can be formed of an insulating material such assilicon oxide (SiO₂), silicon nitride (SiN), or silicon oxynitride tohave a single-layer structure or a stacked-layer structure. The baselayer 103 is formed to have a stacked-layer structure in this embodimentmode. As a first layer of the base layer 103, a layer of siliconoxynitride is formed by plasma CVD using SiH₄, NH₃, N₂O, and H₂ as areactive gas to have a thickness of 10 to 200 nm (preferably 50 to 100nm). In this embodiment mode, a silicon oxynitride layer with athickness of 50 nm is formed as the first layer of the base layer 103.As a second layer of the base layer 103, a layer of silicon oxynitrideis formed by plasma CVD using SiH₄ and N₂O as a reactive gas to have athickness of 50 to 200 nm (preferably 100 to 150 nm). In this embodimentmode, a silicon oxynitride layer with a thickness of 100 nm is formed asthe second layer of the base layer 103.

Next, a first structure layer 105 and a semiconductor layer 104 areformed over the base layer 103 in a first region 21 and a second region22, respectively (a top view of FIG. 1B and a cross-sectional view ofFIG. 1C). The semiconductor layer 104 corresponds to an active layer ina semiconductor element and the first structure layer 105 corresponds toa structure layer in a microstructure. Note that the active layer is asemiconductor layer including a channel formation region, a sourceregion, and a drain region. The semiconductor layer 104 and the firststructure layer 105 can be formed of a material containing silicon suchas a material formed of silicon and a silicon germanium materialcontaining about 0.01 to 4.5 atomic % of germanium. Note that, as thesemiconductor layer 104, a semiconductor having a crystalline structure,a microcrystalline structure, or an amorphous structure can be used.

The material and thickness of the first structure layer 105 can bedecided in view of various factors such as a structure of the structureand a method for package. For example, when a material having a largedifference in distribution of internal stress is used as a material ofthe first structure layer 105, the first structure layer 105 may curve.However, it is possible to form the structure by utilizing the curve ofthe first structure layer 105. In addition when the first structurelayer 105 is formed to be thick, internal stress may be distributed,which causes a curve or buckling. Therefore, the thickness of the firststructure layer 105 is preferably 0.5 to 10 μm.

Next, an insulating layer 106 is formed over the semiconductor layer 104and the first structure layer 105 (a top view of FIG. 1B and across-sectional view of FIG. 1C). The insulating layer 106 serves as agate insulating layer of a semiconductor element. The insulating layer106 can be formed of a material containing silicon such as silicon oxideor silicon nitride by plasma CVD, sputtering, or the like, similarly tothe base layer 103 and can have a single-layer structure or astacked-layer structure. In this embodiment mode, a silicon oxynitridefilm (composition ratio: Si=32%, O=59%, N=7%, and H=2%) is formed tohave a thickness of 115 nm by plasma CVD as the insulating layer 106.

Further, as a material of the insulating layer 106, a metal oxide havinga high dielectric constant, e.g., hafnium (Hf) oxide can also be used.By using such a high dielectric constant material to form a gateinsulating layer, a semiconductor element can be driven at low voltage;thus, a micro-electro-mechanical device with low power consumption canbe provided.

Further, the insulating layer 106 can be formed by a high-density plasmatreatment. A substrate provided with the semiconductor layer 104 and thefirst structure layer 105 is installed into a film formation chambercapable of such a plasma treatment, and the distance between anelectrode for generating plasma, that is, a so-called antenna, and theobject to be treated is set at 20 to 80 mm, and preferably 20 to 60 mmto perform the treatment. Such a high-density plasma treatment allows alow temperature process in which the substrate temperature is 400° C. orless. Accordingly, glass or plastic having low thermostability can beused as the insulating substrate 101.

A film formation atmosphere of such high-density plasma can be anitrogen atmosphere or an oxygen atmosphere. A nitrogen atmosphere istypically a mixed atmosphere of nitrogen and rare gas, or a mixedatmosphere of nitrogen, hydrogen, and rare gas; in which at least one ofhelium, neon, argon, krypton, and xenon is used as the rare gas. Anoxygen atmosphere is typically a mixed atmosphere of oxygen and raregas, a mixed atmosphere of oxygen, hydrogen, and rare gas, or a mixedatmosphere of dinitrogen monoxide and rare gas; in which at least one ofhelium, neon, argon, krypton, and xenon is used as the rare gas.

An insulating layer formed by such a high-density plasma treatment isdense and causes little damage to other films while being formed.Further, the state of an interface to be in contact with the insulatinglayer can be improved. For example, when the gate insulating layer isformed by a high-density plasma treatment, the state of an interfacewith the semiconductor layer can be improved. Accordingly, electricalcharacteristics of the semiconductor element can be improved. Inaddition, when the insulating layer is formed over the structure layeras described above, damage to the structure layer can be reduced informing the insulating layer; thereby maintaining strength of the firststructure layer 105.

Although the case where a high-density plasma treatment is used forforming the insulating layer 106 is described, the high-density plasmatreatment may also be performed to the semiconductor layer. Thehigh-density plasma treatment can modify the surface of thesemiconductor layer. Accordingly, electrical characteristics of thesemiconductor element can be improved.

In addition, the high-density plasma treatment can be used not only forforming the insulating layer 106 but also for forming the base layer 103and another insulating layer.

Next, a conductive layer which serves as a gate electrode 107 of thesemiconductor element is formed over the insulating layer 106 (a topview of FIG. 1D and a cross-sectional view of FIG. 1E). The conductivelayer can be formed by CVD, sputtering, or the like, and processed tohave a predetermined shape. The processing of the conductive layer canbe performed by patterning of a resist and dry etching usingphotolithography. Alternatively, the conductive layer can be formed of acomposition containing a conductive material by droplet discharging. Asthe conductive material, a material such as Ag, Au, Cu, Ni, Pt, Pd, Ir,Rh, W, Al, Ta, Mo, Cd, Zn, Fe, Ti, Si, Ge, Zr, or Ba; ITO (indium tinoxide alloy); ITO containing silicon oxide as a composition (alsoreferred to as ITSO); organoindium; organotin; zinc oxide (ZnO); tinnitride (TiN); or the like can be used. In addition, in the case offorming the conductive layer by droplet discharging, a solvent intowhich the foregoing metal, a dispersive nanoparticle, a silver halideparticle, or the like can be used. By employing the droplet dischargemethod, steps of exposure and development required in photolithographycan be omitted. Note that the droplet discharge method is a method alsoreferred to as an ink-jet method, in which a prepared composition isdischarged from a nozzle in accordance with an electrical signal to forma minute droplet which is, then, attached on a predetermined position.

An end face of the gate electrode 107 may be etched into a taperedshape. In addition, the gate electrode 107 can be formed to have asingle-layer structure or a stacked-layer structure.

Then, impurity elements are added into the semiconductor layer 104 inthe semiconductor element so that an N-type impurity region 111 and aP-type impurity region 110 are formed (a top view of FIG. 2A and across-sectional view of FIG. 2B). Such an impurity region can beselectively formed by forming a mask and adding an impurity elementusing the mask. As a method for adding an impurity element, an iondoping or ion implantation can be employed. As an impurity element whichimparts N-type conductivity, phosphorus (P) or arsenic (As) can betypically used and as an impurity element which imparts P-typeconductivity, boron (B) can be typically used. It is preferable thatrespective impurity elements be added into the N-type impurity region111 and the P-type impurity region 110 at a concentration of 1×10²⁰ to1×10²¹/cm³.

Next, an insulating layer is formed of a nitride compound such assilicon nitride or oxide such as silicon oxide by plasma CVD or thelike, and anisotropically etched in a perpendicular direction so that aninsulating layer 108 being in contact with the side surface of the gateelectrode 107 (hereinafter, referred to as a side wall) is formed (a topview of FIG. 2A and a cross-sectional view of FIG. 2B).

Next, a high-concentration N-type impurity region 109 having impurityconcentration higher than that of the N-type impurity region 111 whichis formed below the side wall 108 is formed by adding an impurityelement to the semiconductor layer 104 including the N-type impurityregion 111. The side wall 108 can prevent short-channel effect which iscaused when the gate length is shortened. This is because an N-typesemiconductor element is more easily affected by short-channel effect.Needless to say, a side wall may be formed and a high-concentrationP-type impurity region may be formed in a P-type semiconductor elementas well.

In addition, in the case where the gate electrode 107 is formed with aplurality of stacked layers with different conductive materials and hasa tapered shape, the N-type impurity region 111 and thehigh-concentration N-type impurity region 109 can also be formed byadding an impurity element once without providing a side wall.

After the impurity regions are formed, a thermal treatment, infraredlight irradiation, or laser irradiation is preferably performed in orderto activate the impurity elements. Furthermore, at the same time as theactivation, plasma damage to the insulating layer 106 and plasma damageto the interface between the insulating layer 106 and the semiconductorlayer 104 can be restored. In particular, effective activation can beperformed when the impurity elements are activated using an excimerlaser from the front or the back surface in an atmosphere at atemperature ranging from room temperature to 300° C. Further, a higherharmonic such as a second harmonic of a YAG laser may be used for theactivation. A YAG laser is preferable to be used for the activationbecause maintenance of the YAG laser is not so frequently required.

Further, a passivation film of an insulating layer such as a siliconoxynitride film or silicon oxide film may be formed to cover the gateelectrode and the semiconductor layer. After that, a thermal treatment,infrared light irradiation, or laser irradiation may be performed toconduct hydrogenation. For example, a silicon oxynitride film is formedas a passivation film by plasma CVD, and then heated using a clean ovenat 300 to 550° C. for 1 to 12 hours, thereby hydrogenating thesemiconductor layer. By performing this step, dangling bonds in thesemiconductor layer which are generated when the impurity elements areadded can be terminated by hydrogen contained in the passivation film.At the same time, the activation treatment of the foregoing impurityregions can be performed.

Through the foregoing steps, an N-type semiconductor element 112 and aP-type semiconductor element 113 are formed (a top view of FIG. 2A and across-sectional view of FIG. 2B). At this time, an impurity region isformed in the structure layer 105 included in a microstructure. In thisembodiment mode, an N-channel thin film transistor and P-channel thinfilm transistor are employed as an N-type semiconductor element andP-type semiconductor element, respectively.

Subsequently, an insulating layer 114 is formed to cover the entiresurface (a top view of FIG. 2C and a cross-sectional view of FIG. 2D).The insulating layer 114 can be formed of an inorganic material havingan insulating property or an organic material having an insulatingproperty. As the inorganic material, silicon oxide, or silicon nitridecan be used. As the organic material, polyimide, acrylic, polyamide,polyimide amide, a resist, benzocyclobutene, siloxane, or polysilazanecan be used. Siloxane includes a skeleton structure formed by a bond ofsilicon (Si) and oxygen (O). An organic group containing at leasthydrogen (such as an alkyl group or aromatic hydrocarbon) is used as asubstituent. In addition, a fluoro group may be used as the substituent.Alternatively, a fluoro group and an organic group including at leasthydrogen may be used as the substituent. Note that polysilazane isformed using a polymer material having a bond of silicon (Si) andnitrogen (N) as a starting material.

Next, the insulating layers 114 and 106 are etched sequentially to forma contact hole 115 (a top view of FIG. 2C and a cross-sectional view ofFIG. 2D). The etching may be dry etching or wet etching. In thisembodiment mode the contact hole 115 and an opening 116 are formed bydry etching. The opening 116 is surrounded by the side surface of thecontact hole in the insulating layer 114 and the first structure layer105 exposed by the contact hole.

Here, the opening 116 is a space required for moving a microstructure.Conventionally, the space is formed by etching a sacrifice layer ordeeply etching a silicon wafer. In the present invention however, thespace is formed by processing an insulating layer which is formed in amanufacturing process of a semiconductor element. Therefore, themanufacturing process can be simplified, which leads to improvement inproduction efficiency and reduction in cost.

In addition, an insulating layer may be formed of a nitride compoundsuch as silicon nitride or oxide such as silicon oxide by plasma CVD onthe side surface of the opening 116. Alternatively, a metal layer may beformed by sputtering on the side surface of the opening 116. At thattime, an insulating layer or a metal layer is probably formed on thebottom surface of the opening 116 as well. The insulating layer or ametal layer may be etched to be removed, if not necessary. With such astructure, change in pressure in the space of themicro-electro-mechanical device, which is caused due to pressure appliedthereto when the micro-electro-mechanical device is driven or gasgenerated from the insulating layer 114 because of change in temperatureof the micro-electro-mechanical device can be prevented.

Next, a conductive layer 117, which serves as a source electrode or adrain electrode is formed over the insulating layer 114 and in thecontact hole 115. In addition, a second structure layer 118 is formed (atop view of FIG. 3A and a cross-sectional view of FIG. 3B). At thistime, a wire included in an electrical circuit can be formed.

The conductive layer 117 and the second structure layer 118 can beformed of aluminum (Al), titanium (Ti), molybdenum (Mo), tungsten (W),or silicon (Si), or a conductive material such as an alloy materialusing any of the foregoing elements. A composition containing one or aplurality of conductive materials is ejected by droplet discharging toform the second structure layer 118 and the conductive layer 117 whichforms a source or drain electrode. Alternatively, the foregoingconductive material by sputtering or CVD may be deposited and thenprocessed into a predetermined shape to form the conductive layer 117which forms a source or drain electrode. The processing of theconductive material can be performed by patterning of a resist and dryetching using photolithography.

The material and thickness of the second structure layer 118 can bedecided in consideration of various factors such as a structure of thestructure and a method for package. The second structure layer 118 ispreferably formed to have a thickness of 0.5 to 10 μm.

In addition, when the source electrode and the drain electrode have apattern with a corner when seen from the top, they are preferably etchedso that the corner is round. Accordingly, occurrence of dust can besuppressed, thus the yield can be improved. This is similarly applied tothe case of etching a conductive layer such as the gate electrode 107.

Next, an insulating layer 119 serving as a protective film is formed bySOG (Spin On Glass), droplet discharging, or the like so as to cover asemiconductor element portion (a top view of FIG. 3C and across-sectional view of FIG. 3D). The insulating layer 119 can be formedof an inorganic material or an organic material. For example, theinsulating layer 119 is formed with a film containing carbon such as DLC(Diamond Like Carbon), a film containing silicon nitride, a filmcontaining silicon nitride oxide, an epoxy resin, or the like. Since theinsulating layer 119 is thick, an organic material such as an epoxyresin is preferably used so that the insulating layer 119 does not loseits flexibility. The insulating layer can be formed to have asingle-layer structure or a stacked-layer structure. In the case of astacked-layer structure, an inorganic material and an organic materialare preferably stacked alternately.

Then, the peeling layer 102 is exposed by processing the insulatinglayers 114 and 119 by photolithography or laser light irradiation toform an opening 120 for peeling the peeling layer 102. In addition,openings 121 and 122 are formed so that the first structure layer 105and the second structure layer 118 are exposed, respectively (FIG. 4A).The openings 121 and 122 can be formed by etching or laser irradiationsimultaneously or sequentially.

Then, the peeling layer 102 is removed by pouring an etchant into theopening 120 (FIG. 4B). As the etchant, a gas or a liquid containinghalogen fluoride or a halogen compound is used. For example, the peelinglayer 102 is removed by using chlorine trifluoride (ClF₃) as the gascontaining halogen fluoride. Accordingly, a micro-electro-mechanicaldevice forming portion 123 is separated from the insulating substrate101 (FIG. 4C). Note that the micro-electro-mechanical device formingportion includes a region in which a functional element is formed. Thepeeling layer 102 may be partially left without being removed entirely.By leaving a part of the peeling layer 102, consumption of the etchantis suppressed and time taken for removing the peeling layer can beshortened. In addition, by leaving a part of the peeling layer 102, themicro-electro-mechanical device forming portion 123 can be kept over theinsulating substrate 101 after removing the peeling layer 102.

It is preferable to reuse the insulating substrate 101 after themicro-electro-mechanical device forming portion 123 is separated forreducing the cost. In addition, the insulating layer 119 is formed toprevent the micro-electro-mechanical device forming portion 123 fromscattering after the peeling layer 102 is removed. After the peelinglayer 102 is removed, the micro-electro-mechanical device formingportion 123, which is small, thin, and light, easily scatters since itis not attached firmly to the insulating substrate 101. However, byforming the insulating layer 119 over the micro-electro-mechanicaldevice forming portion 123, the micro-electro-mechanical device formingportion 123 receives weight and scattering thereof from the insulatingsubstrate 101 can be prevented. In addition, by forming the insulatinglayer 119, the micro-electro-mechanical device forming portion 123 whichis thin and light is not rolled due to stress after being separated fromthe insulating substrate 101, and the strength thereof can be ensured toa certain extent.

Subsequently, one surface of the micro-electro-mechanical device formingportion 123 is attached to a first sheet member 124, and completelyseparated from the insulating substrate 101 (FIG. 5A). In the case wherea part or the peeling layer 102 is left without being removed entirely,the micro-electro-mechanical device forming portion 123 is separatedfrom the insulating substrate 101 by physical means.

In the above step, when adhesion between the micro-electro-mechanicaldevice forming portion 123 and the peeling layer 102 is weak, the stepof removing the peeling layer 102 may be omitted and themicro-electro-mechanical device forming portion 123 can be separatedfrom the insulating substrate 101 by physical means.

Next, a second sheet member 125 is provided to the other surface of themicro-electro-mechanical device forming portion 123 and either or bothheat treatment and pressure treatment is performed so that the secondsheet member 125 adheres thereto. This step is referred to as transferto the second sheet member 125. Upon providing or after providing thesecond sheet member 125, the first sheet member 124 is separated (FIG.5B). The second sheet member 125 is formed of an organic material withhigh flexibility such as acrylic. Such a sheet is referred to as a resinsubstrate (flexible substrate) as well.

Then, the second sheet member 125 is folded so that the first structurelayer 105 formed in the first region and the second structure layer 118formed in the second region, in the micro-electro-mechanical deviceforming portion 123 formed over the second sheet member 125 face eachother and are sealed so as to be overlapped each other at leastpartially (FIG. 5C). By performing such a step, a space 129 isgenerated. That is, the space 129 is formed by the openings 121 and 122which are opposite to each other. At this time, in a region other thanthe openings 121 and 122, the insulating layer 119 is folded so that thesurface thereof comes into contact; therefore, it is preferable that theinsulating layer 119 have an adhesion property. In addition, theinsulating layer 119 is preferably formed of an organic material inorder to reduce the impact of being folded. When an organic material isused for the insulating layer 119, the film thickness can be thickcompared with when an inorganic material is used. Further, since anorganic material has low hardness, the impact after completion of theproduct can be also reduced.

In addition, the space 129 may be closed by being sealed or may beopened. When the space is closed, a reference pressure is sealed thereinand the space can be used as a pressure sensor.

In the present invention, since the microstructure is folded to form aspace, the semiconductor element is formed in a region where thecurvature radius is none or the curvature is large, in consideration ofa material of the insulating substrate. That is, the semiconductorelements are formed in a region in which the semiconductor element canbe driven when the microstructure is folded.

Thus, the microstructure 126 and the semiconductor elements 127 and 128are formed over one surface (FIG. 5C). By manufacturing themicrostructure and the semiconductor element over one surface andsimplifying the steps of forming the space for moving the microstructureand of packaging the microstructure and semiconductor element, amicro-electro-mechanical device with low manufacturing cost and improvedproduction efficiency can be provided.

A micro-electro-mechanical device including a microstructure of thisembodiment mode can be applied to a sensor, a memory, a fractionationdevice, a discharge device, or a pressure sensor, which are described infollowing embodiment modes. Needless to say, the microstructure can beemployed as a minute pump such as a gas component suction device withoutbeing limited to a discharge device.

In addition, a structure may be employed, in which amicro-electro-mechanical device is covered with a film or the like to beprotected in accordance with a type of the micro-electro-mechanicaldevice and the intended purpose.

Embodiment Mode 2

In this embodiment mode, a semiconductor layer having a crystallinestructure, a microcrystalline structure, or an amorphous structure canbe applied to the structure layer. In this embodiment mode, the casewhere polycrystalline silicon is used for the structure layer isdescribed. Note that the structure layer may have a stacked-layerstructure. When polycrystalline silicon is used for such a structurelayer, polycrystalline silicon may be contained any of the layers. Thestructure layer can be also referred to as a layer containingpolycrystalline silicon. Similarly, in the case of amorphous silicon,the structure layer can be also referred to as a layer containingamorphous silicon.

First, an amorphous silicon layer is formed over a surface for forming astructure layer. Then a thermal treatment is performed to crystallizethe amorphous silicon layer, thereby a polycrystalline silicon layer canbe obtained. A heating furnace, laser irradiation, irradiation withlight emitted from a lamp in stead of laser light (hereinafter referredto as lamp annealing), or a combination thereof can be employed as thethermal treatment.

A continuous wave laser beam (hereinafter referred to as a CW laserbeam) or a pulsed wave laser beam (hereinafter referred to as a pulsedlaser beam) can be used in the case of the laser irradiation. One of ora plurality of an Ar laser, a Kr laser, an excimer laser, a YAG laser, aY₂O₃ laser, a YVO₄ laser, a YLF laser, a YAlO₃ laser, a glass laser, aruby laser, an alexandrite laser, a Ti:sapphire laser, a copper vaporlaser, and a gold vapor laser can be used. Crystals having a large grainsize can be obtained by irradiation with a laser beam of a fundamentalwave of the above laser beam or a second harmonic to a fourth harmonicof the fundamental wave. For example, a second harmonic (532 nm) or athird harmonic (355 nm) of an Nd:YVO₄ laser (fundamental wave: 1064 nm)can be used. Energy density of the laser at this time needs to be about0.01 to 100 MW/cm² (preferably, 0.1 MW/cm² to 10 MW/cm²). The laserirradiation is performed at scanning speed of about 10 to 2000 cm/sec.

Note that the amorphous silicon layer may be irradiated with acontinuous wave laser beam at a fundamental wave and a continuous wavelaser beam at a higher harmonic, or may be irradiated with a continuouswave laser beam at a fundamental wave and a pulsed wave laser beam at ahigher harmonic. Energy can be supplemented by irradiation with pluralkinds of laser beams.

Further, in the case of a pulsed wave laser, pulsed laser may beoscillated with such a repetition rate that the laser of the next pulseis emitted until the semiconductor film is solidified after thesemiconductor film is melted. By oscillating the laser beam with such arepetition rate, crystal grains that are continuously grown in thescanning direction can be obtained. Specifically, a laser beam with arepetition rate of 10 MHz or more is used, which is much higher than therepetition rate band of several tens to several hundreds Hz which isnormally used.

Alternatively, in the case of using a heating furnace for the thermaltreatment, the amorphous silicon layer is heated at a temperature of 400to 550° C. for 2 to 20 hours. At this time, the temperature may be setin stages in the range of 400 to 550° C. so as to be graduallyincreased. Since hydrogen or the like of the amorphous silicon layer isreleased by the first low-temperature heating step at about 400° C.,film roughness in crystallization can be reduced.

In addition, a metal element which promotes crystallization, e.g., Ni,may be formed over the amorphous silicon layer, which is preferable inthat the heat temperature can be lowered. As the metal element, Fe, Ru,Rh, Pd, Os, Ir, Pt, Cu, Au, or the like can also be used.

Further, in addition to the thermal treatment, irradiation with theforegoing laser beam may be performed to form the polycrystallinesilicon layer.

Polycrystalline silicon which has been crystallized using such a metalcan have higher tenacity than polycrystalline silicon which is formed bycrystallization without a metal. This is because crystal grainboundaries of polycrystalline silicon become continuous due to thecrystallization using a metal. The polycrystalline silicon in whichcrystal grain boundaries are continuous has such a structure thatcovalent bonds are not broken at grain boundaries, unlikepolycrystalline silicon obtained by crystallization without a metal.Accordingly, stress concentration which is caused by defects due tograin boundaries does not occur. As a result, fracture stress becomeshigher than that of the polycrystalline silicon formed bycrystallization without a metal.

Polycrystalline silicon where crystal grain boundaries are continuoushas high-electron mobility, which is suitable as the material in thecase where a microstructure is controlled by electrostatic force e.g.,electrostatic attractive force. Furthermore, the structure layercontains a metal element which promotes crystallization and has aconductive property; therefore, it is suitable for amicro-electro-mechanical device of the present invention in which astructure is controlled by electrostatic force. Needless to say, apolycrystalline silicon layer may be applied to the structure layer inthe case where the microstructure is controlled by electromagneticforce.

In addition, when nickel is used as the metal, nickel silicide may beformed depending on the concentration of nickel. It is generally knownthat a silicon alloy such as nickel silicide exhibits high mechanicalstrength. Therefore, by leaving the metal used in the thermal treatmentin the entire or a part of the silicon layer and applying appropriatethermal treatment, a microstructure with higher hardness and a higherconductive property can be formed.

The layer having nickel silicide in which the metal used in theforegoing crystallization is left (nickel silicide layer) and apolycrystalline silicon layer are stacked, thereby obtaining a structurelayer which is superior in the conductive property and is flexible. Itis generally known that a silicon alloy such as nickel silicide exhibitshigh mechanical strength. Therefore, by leaving the metal used in thecrystallization of the semiconductor layer entirely of partially in thesemiconductor layer and applying appropriate thermal treatment, astructure with higher hardness and a higher conductive property can beformed. By stacking a nickel silicide layer and an amorphous siliconlayer, a hard material which is superior in the conductive property canbe obtained.

Such a silicide layer can also be formed of tungsten, titanium,molybdenum, tantalum, cobalt, or platinum as well as nickel, whichcorrespond to a tungsten silicide layer, a titanium silicide layer, amolybdenum silicide layer, a tantalum silicide layer, a cobalt silicidelayer, and a platinum silicide layer, respectively. Among them, cobaltor platinum can also be used as a metal for reducing the heattemperature.

However, since the metal for promoting crystallization is a contaminantfor a micro-electro-mechanical device, it can be removed after thecrystallization. In this case, after crystallization by thermaltreatment or laser irradiation, a layer to be a gettering sink is formedover the silicon layer and heated, thereby moving the metal element intothe gettering sink. A semiconductor layer into which an impurity isadded or a polycrystalline semiconductor layer can be used as thegettering sink. For example, an amorphous semiconductor layer into whichan inert element such as argon is added and which is formed over thesemiconductor layer may be used as a gettering sink. By adding an inertelement, distortion can be generated in the amorphous semiconductorlayer, and a metal element can be efficiently captured by thedistortion. Alternatively, the metal can be captured by forming asemiconductor layer into which another element such as phosphorus isadded.

In the case where a conductive property is required for the structurelayer, an impurity element such as phosphorus, arsenic, or boron canalso be added after the metal is removed. A structure having aconductive property is suitable for a micro-electro-mechanical device ofthe present invention which is controlled by electrostatic force. Notethat the metal may be left in the structure layer without being removed.

The structure layer may have a stacked-layer structure in order toobtain a required thickness. For example, a polycrystalline siliconlayer can be formed to have a stacked-layer structure by repeatingformation of an amorphous silicon layer and crystallization by thermaltreatment. By this thermal treatment, a stress in the polycrystallinesilicon layer which has been formed before is suppressed; therebypeeling of a film and deformation of the substrate can be prevented.Further, in order to further suppress the stress in the film, etching ofthe silicon layer may also be included in the repeated steps. Such aforming method including etching is suitable for the case where amaterial having a large internal stress is used for the structure layer.

In the case where crystallization is performed by using a metal asdescribed above, the crystallization can be performed at a lowtemperature compared with crystallization without a metal, therefore,more kinds of materials can be given as a material for a substrateincluded in a microstructure. For example, in the case where thesemiconductor layer is crystallized only by heat, it is required thatthe layer is heated at about 1000° C. for about one hour, thus a glasssubstrate which is weak in heat cannot be used. However, by performingcrystallization using the foregoing metal as in this embodiment mode, aglass substrate with a distortion point of 593° C. can be used.

In crystallization using a metal as the foregoing step, a partialcrystallization can be performed as well by selectively applying(adding)) the metal.

In such crystallization, partial crystallization can be performed bychange in a laser condition and partial irradiation.

Various combinations of materials can be obtained by the foregoingpartial crystallization. For example, only a portion which is drivenfrequency may be crystallized to increase tenacity.

Note that a polycrystalline silicon layer can be similarly used for thesecond structure layer 118.

This embodiment mode can be freely combined with the foregoingembodiment modes.

Embodiment Mode 3

In the present invention, silicon or silicon compounds having variousproperties can be stacked for the structure layer. Silicon layers havingvarious properties are different in properties such as strengthdepending on the crystalline structure which is selected from anamorphous structure, microcrystalline structure, polycrystallinestructure, or the like. Further, in the case of polycrystallinestructure, a silicon layer thereof is different in properties due to thecrystal direction. In this embodiment mode, an example of astacked-layer structure used for the structure layer is described.

As shown in FIG. 6, silicon and silicon compounds which are differentfrom each other in properties can be stacked. FIG. 6 shows the casewhere an amorphous silicon layer 150, a polycrystalline silicon layer151, and a nickel silicide layer 152 are stacked as the structure layer118 to form a space 153. Thus, by stacking layers different inmechanical properties, the structure layer 118 as needed can beobtained. In addition, the space 153 is formed by two openings oppositeto each other like the above embodiment modes. At this time, in a regionother than the openings, the insulating layer is folded so that thesurface thereof comes into contact; therefore, it is preferable that theinsulating layer have an adhesion property. In addition, when theinsulating layer is formed of an organic material, impact of beingfolded and the impact after completion of the product can be alsoreduced.

In addition, the space 153 may be closed by being sealed or may beopened. When the space is closed, a reference pressure is sealed thereinand the space can be used as a pressure sensor.

As a layer for the structure, etching may be performed after stackingall the layers or every time a film is formed. Thus, the structure layer118 having a required property can be easily formed.

Note that balance between flexibility and hardness can be determined bya ratio of respective thicknesses of the stacked layers. This is becausedestruction, which occurs from dangling bonds in the amorphous siliconlayer, would be stopped by a polycrystalline silicon layer because thepolycrystalline silicon layer having a high crystalline property doesnot propagate destruction easily. Therefore, the amorphous silicon layercan be formed to be relatively thick and the polycrystalline siliconlayer can be formed to be relatively thin.

Further, crystal growth of silicon proceeds in a perpendicular directionwith respect to a substrate when laser crystallization is performedusing a metal, whereas crystal growth of silicon proceeds in a paralleldirection with respect to a substrate when laser crystallization isperformed without a metal. By stacking layers formed by both kinds ofthe laser crystallization, a material which is further superior intenacity can be obtained. Since layers having different crystaldirections are stacked, if a crack or the like occurs in one layer, thecrack is not easily propagated to another layer having a differentcrystal direction; accordingly, the structure layer with high strengthcan be formed.

The amorphous silicon layer, the polycrystalline silicon layer, or thenickel silicide containing layer as described above can also be stackedby repeating film formation, in order to provide a necessary thickness.For example, formation of the amorphous silicon layer and heating may berepeated. Alternatively, etching of the silicon layer may also beincluded in the repeated steps in order to suppress the stress in thefilm; in this case, formation, heating, and patterning of the amorphoussilicon layer are repeatedly performed. As a result peeling of theamorphous silicon layer formed over the insulating substrate can beprevented. The film formation and the crystallization can be combined byfreely selecting among the foregoing examples.

By stacking semiconductor layers as described above, a structure layerhaving both flexibility and hardness can be obtained.

Note that similar stacked-layer structure can be applied to the secondstructure layer 118.

This embodiment mode can be freely combined with the foregoingembodiment modes.

Embodiment Mode 4

In this embodiment mode, a method in which micro-electro-mechanicaldevices formed over one substrate are assembled is described.

A mark for alignment 160 is provided in advance over the second sheetmember 125 where the micro-electro-mechanical device forming portion 123is formed (FIG. 7A).

Then, the second sheet member 125 is folded by physical means withreference to the mark for alignment 160 (FIG. 7B). With this step, amicrostructure with a space for moving the microstructure and asemiconductor element for controlling the microstructure as shown inFIG. 5C can be assembled.

Although in FIGS. 7A and 7B, an example where the second sheet member125 is folded in half with reference to the mark for alignment 160 alonga central line; a type, a shape, a size, a number, and a place of themark for alignment are appropriately selected. A folding pattern of thesheet member can be appropriately chosen.

In addition, the micro-electro-mechanical device forming portion can beassembled by using different means from described above. For example,the second sheet member 125 is cut out with the micro-electro-mechanicaldevice forming portion 123 as a minimum unit (FIG. 8A).

Then, the cut micro-electro-mechanical device forming portion 123 isfolded reference to the mark for alignment 161 provided in advance (FIG.8B). With this step, a microstructure with a space for moving themicrostructure and a semiconductor element for controlling themicrostructure as shown in FIG. 5C can be assembled.

Although in FIGS. 8A and 8B, an example where themicro-electro-mechanical device forming portion 123 is folded in halfwith reference to the mark for alignment 161 along a central line; atype, a shape, a size, a number, and a place of the mark for alignmentare appropriately selected. A folding pattern of themicro-electro-mechanical device forming portion can be appropriatelychosen.

Although in FIGS. 8A and 8B, an example where the minimum unit to be cutout is one of the micro-electro-mechanical device forming portions 123is shown, the minimum unit to be cut out may be a plurality of themicro-electro-mechanical device forming portions 123.

In this embodiment mode, a groove can be preformed in a border withwhich the micro-electro-mechanical device forming portion is folded. Thegroove can be formed by physical means such as laser scribing or acutter, chemical means utilizing chemical reaction, or the like. In thatcase, a mark for alignment is not necessarily provided because thegroove can serve as a fiducial mark.

Embodiment Mode 5

In this embodiment mode, a method for forming a microstructure and asemiconductor element over one surface, which is different from that ofEmbodiment Mode 1 is described with reference to the drawings. In thedrawings, top views and cross-sectional views taken along a line O-P areshown.

First, a peeling layer 202 is formed over an insulating substrate 201and a base layer 203 is formed thereover like Embodiment Mode 1 (FIG.9A).

A semiconductor layer 204 and a first structure layer 205 are formedover the base film 203 (a top view of FIG. 9B and a cross-sectional viewof FIG. 9C). The semiconductor layer 204 and the first structure layer205 can be formed similarly to Embodiment Mode 1. In addition, as thesemiconductor layer 204 and the first structure layer 205, a siliconlayer having a crystalline structure, a microcrystalline structure, oran amorphous structure can be used.

Next, an insulating layer 206 is formed over the semiconductor layer 204and the first structure layer 205 (a top view of FIG. 9B and across-sectional view of FIG. 9C). The insulating layer 206 serves as agate insulating layer of a semiconductor element. Similarly toEmbodiment Mode 1, the insulating layers and the like can be formed byhigh-density plasma.

Similarly to Embodiment Mode 1, a conductive layer is formed over theinsulating layer 206 to form a gate electrode 207 of the semiconductorelement (a top view of FIG. 9D and a cross-sectional view of FIG. 9E).

Then, similarly to Embodiment Mode 1, impurity elements are added intothe semiconductor layer 204 in the semiconductor element so that anN-type impurity region 211 and a P-type impurity region 210 are formed(a top view of FIG. 10A and a cross-sectional view of FIG. 10B).

Next, an insulating layer is formed of a nitride compound such assilicon nitride or oxide such as silicon oxide by plasma CVD or thelike, and anisotropically etched in a perpendicular direction so that aninsulating layer being in contact with the side surface of the gateelectrode 207, that is, a side wall 208 is formed (a top view of FIG.10A and a cross-sectional view of FIG. 10B). The side wall 208 canprevent short-channel effect which is caused when the gate length isshortened.

Next, a high-concentration N-type impurity region 209 having impurityconcentration higher than that of the N-type impurity region 211 whichis formed below the side wall 208 is formed by adding an impurityelement to the semiconductor layer 204 including the N-type impurityregion 211. With this step, an N-type semiconductor element 212 and aP-type semiconductor element 213 can be formed (a top view of FIG. 10Aand a cross-sectional view of FIG. 10B). At this time, an impurityregion is also formed in the first structure layer 205 included in themicrostructure.

Subsequently, an insulating layer 214 is formed to cover the entiresurface (a top view of FIG. 10C and a cross-sectional view of FIG. 10D).Then, the insulating layer 214 can be formed of an inorganic materialhaving an insulating property, an organic material having an insulatingproperty, or the like.

Next, the insulating layers 214 and 206 are etched sequentially to forma contact hole 215 (a top view of FIG. 10C and a cross-sectional view ofFIG. 10D). The etching may be dry etching or wet etching. In thisembodiment mode the contact hole 215 is formed by dry etching.

Next, a conductive layer, which serves as a source electrode or a drainelectrode 217, is formed over the insulating layer 214 and in thecontact hole 215. In addition, a second structure layer 218 is formed (atop view of FIG. 11A and a cross-sectional view of FIG. 11B). In thistime, a wire included in an electrical circuit can be formed.

Next, an insulating layer 219 serving as a protective film is formed bySOG, droplet discharging, or the like so as to cover a semiconductorelement portion (a top view of FIG. 11C and a cross-sectional view ofFIG. 11D). The insulating layer 219 can be formed of an inorganicmaterial or an organic material. For example, the insulating layer 219is formed with a film containing carbon such as DLC (Diamond LikeCarbon), a film containing silicon nitride, a film containing siliconnitride oxide, an epoxy resin, or the like. Since the insulating layer219 is thick, an organic material such as an epoxy resin is preferablyused so that the insulating layer 219 does not lose its flexibility. Theinsulating layer 219 can be formed to have a single-layer structure or astacked-layer structure. In the case of a stacked-layer structure, aninorganic material and an organic material are preferably stackedalternately.

Then, the peeling layer 202 is exposed by processing the insulatinglayer by photolithography or laser light irradiation to form an opening220 for peeling the peeling layer 202(FIG. 12A).

Then, the peeling layer 202 is removed by pouring an etchant into theopening 220 (FIG. 12B). As the etchant, a gas or a liquid containinghalogen fluoride or a halogen compound is used. When the etchant ispoured, a micro-electro-mechanical device forming portion 221 isseparated from the insulating substrate 201 (FIG. 12C).

Subsequently, one surface of the micro-electro-mechanical device formingportion 221 is attached to a first sheet member 222, and completelyseparated from the substrate 201 (FIG. 13A). In the case where a part ofthe peeling layer 202 is left without being removed entirely, themicro-electro-mechanical device forming portion 221 is separated fromthe insulating substrate 201 by physical means.

In the foregoing steps, when adhesion between themicro-electro-mechanical device forming portion 221 and the peelinglayer 202 is weak, the step of removing the peeling layer 202 may beomitted and the micro-electro-mechanical device forming portion 221 canbe separated from the insulating substrate 201 by physical means.

Next, the second sheet member 225 provided with openings 223 and 224 isattached to the other surface of the micro-electro-mechanical deviceforming portion 221 and either or both heat treatment and pressuretreatment are performed so that the second sheet member 225 adheresthereto. Upon providing or after providing the second sheet member 225,the first sheet member 222 is separated (FIG. 13B). At that time, theopenings 223 and 224 of the second sheet member 225 are provided in aposition corresponding to the first structure layer 205 and the secondstructure layer 218, respectively. In addition, an insulating layer of anitride compound such as silicon nitride or oxide such as silicon oxideformed by CVD or the like or a metal layer formed by sputtering or thelike may be formed on the side surface of the opening portions 223 and224. The metal layer formed on the side surface can be used as a wire.

Then, the second sheet member 225 is folded so that the first structurelayer 205 and the second structure layer structure layer 218 in themicro-electro-mechanical device forming portion 221 formed over thesecond sheet member 225, are opposite to each other (FIG. 13C). That is,the space 229 is formed by the openings 223 and 224 which are oppositeto each other. At this time, in a region other than the openings 223 and224, the second sheet member 225 is folded so that the surface thereofcomes into contact; therefore, it is preferable that the second sheetmember 225 have an adhesion property. In addition, the second sheetmember 225 is preferably formed of an organic material in order toreduce the impact of being folded. When an organic material is used forthe second sheet member 225, the film thickness can be thick comparedwith when an inorganic material is used. Further, since an organicmaterial has low hardness, the impact after completion of the productcan also be reduced.

In addition, a space 229 may be closed by being sealed or may be opened.When the space is closed, a reference pressure is sealed therein and thespace can be used as a pressure sensor.

With these steps, the space 229 whose side surface is surrounded by thesecond sheet member 225 and the top and bottom surfaces are surroundedby the base layer 203, that is, the space 229 which is surrounded by thesecond sheet member 225 and the base layer 203 is formed. Thus, themicrostructure 226 and the semiconductor elements 227 and 228 are formedover one surface (FIG. 13C). By manufacturing the microstructure and thesemiconductor element over one surface and simplifying the steps offorming the space for moving the microstructure and of packaging themicrostructure and semiconductor element, a micro-electro-mechanicaldevice with low manufacturing cost and improved production efficiencycan be provided.

In addition, a structure may be employed, in which amicro-electro-mechanical device is covered with a film or the like to beprotected in accordance with a type of the micro-electro-mechanicaldevice and the intended purpose.

This embodiment mode can be freely combined with the foregoingembodiment modes.

Embodiment Mode 6

In this embodiment mode, an example of the structure of themicro-electro-mechanical device is described with reference to thedrawings.

A schematic diagram of the micro-electro-mechanical device of thepresent invention is shown in FIG. 14. A micro-electro-mechanical device11 of the present invention includes an electric circuit portion 12including a semiconductor element and a structure portion 13 constitutedfrom a microstructure. The electric circuit portion 12 includes acontrol circuit 14 for controlling the microstructure, an interface 15for communicating with an external control device 10, and the like. Thestructure portion 13 includes a sensor 16, an actuator 17, a switch, andthe like by using the microstructure.

An actuator refers to a component element for converting a signal(mainly an electrical signal) into a physical quantity.

Further, the electric circuit portion 12 can also include a centralprocessing unit or the like for processing information obtained by thestructure portion 13.

The external control device 10 performs operation such as transmitting asignal for controlling the micro-electro-mechanical device 11, receivinginformation obtained by the micro-electro-mechanical device 11, andsupplying driving power to the micro-electro-mechanical device 11.

The invention is not limited to the above examples of structures. Thatis, a micro-electro-mechanical device of the present invention includesan electric circuit having a semiconductor element and controlling amicrostructure, and the microstructure controlled by the electriccircuit.

Conventionally, in the case of handling a minute object with a size ofmillimeter or smaller, a process has been required in which thestructure of the minute object is enlarged, a person or a computerobtains its information to determine the data processing and operation,and the operation is reduced and transmitted to the minute object.

However, the micro-electro-mechanical device of the present inventionwhich is described above allows operation of a minute object just by aperson or a computer supplying a broader instruction. That is, when aperson or a computer determines a purpose and transmits an instruction,the micro-electro-mechanical device can obtain and process informationon an object by using a sensor or the like, and operate accordingly.

In the above example, the object is assumed to be minute. This includes,for example, a case where a size of object itself is in several metersbut a signal sent therefrom is a small signal (e.g., a small change inlight or pressure).

The micro-electro-mechanical device of the present invention is in thefield of micromachines, and the size of the unit ranges from micrometersto millimeters. Further, in the case of manufacturing themicro-electro-mechanical device as a component to be incorporated inanother mechanical apparatus, the micro-electro-mechanical device mayhave the size with of several meters so as to be able to handle easilyin assembly.

Embodiment Mode 7

In this embodiment mode, an example of the micro-electro-mechanicaldevice described in the above embodiment modes is described. Themicro-electro-mechanical device of the present invention can be includedin a sensor device in which a sensor element is formed with amicrostructure.

FIG. 15A shows a structure of a sensor device 301 which is one exampleof the micro-electro-mechanical device of the present invention. Thesensor device 301 of this embodiment mode includes an electric circuitportion 302 including a semiconductor element and a structure portion303 constituted from a microstructure.

The structure portion 303 includes a sensor element 304 constituted froma microstructure, which detects external pressure, concentration of asubstance, a flow rate of gas or fluid, or the like.

The electric circuit portion 302 includes an A/D converting circuit 305,a control circuit 306, an interface 307, a memory 308, and the like.

The A/D converting circuit 305 converts information transmitted from thesensor element into a digital signal. The control circuit 306 controlsthe A/D converting circuit so that, for example, the digital signal isstored in the memory. The interface 307 receives driving power or acontrol signal from an external control device 310, or transmits sensinginformation to the external control device 310, or the like. The memory308 stores sensing information, information specific to the sensordevice, or the like.

Further, the electric circuit portion 302 can also include an amplifiercircuit for amplifying a signal received from the structure portion 303,a central processing unit for processing information obtained by thestructure portion 303, or the like.

The external control device 310 performs operation such as transmittinga signal for controlling the sensor device 301 and receiving informationobtained by the sensor device 301, or supplying driving power to thesensor device 301.

With the sensor device 301 having the above structure, externalpressure, concentration of a substance, a flow rate of gas or fluid,temperature, or the like can be detected. Further, in the case where thesensor device includes a central processing unit, a sensor device inwhich detected information is processed in the sensor device and acontrol signal for controlling another device is generated andoutputted, can also be realized.

FIG. 15B is a cross-sectional view showing an example of a structure ofthe sensor element 304. The sensor element 304 shown in FIGS. 15A and15B is a capacitor including a space 323, a first conductive layer 320as a first structure layer in the foregoing embodiment modes, and asecond conductive layer 321 as a second structure layer in the foregoingembodiment modes. Further, since the space 323 is provided, the firstconductive layer 320 can be moved by electrostatic force, pressure, orthe like. That is, the sensor element 304 is a variable capacitor inwhich the distance between the first conductive layer and the secondconductive layer changes, which means the space changes in shape.

In addition, the space 323 may be closed by being sealed or may beopened. When the space is closed, a reference pressure is sealed thereinand the space can be used as a pressure sensor.

Utilizing this structure, the sensor element 304 can be used as apressure sensor element in which the first conductive layer 320 is movedby pressure.

In addition, in the sensor element 304 shown in FIG. 15B, the firstconductive layer 320 can be formed by stacking two kinds of substanceshaving different coefficients of thermal expansion. In this case, sincethe first conductive layer 320 is moved by temperature change, thesensor element 304 can be used as a temperature sensor element.

The present invention is not limited to the above structure. That is,according to this embodiment mode, a sensor device includes an electriccircuit which includes a semiconductor element and controls amicrostructure, and a sensor element which is constituted from themicrostructure controlled by the electric circuit and detects somephysical quantity. Further, the sensor device is manufactured by themanufacturing method described in any one of the foregoing embodimentmodes.

This embodiment mode can be freely combined with the foregoingembodiment modes.

Embodiment Mode 8

In this embodiment mode, a specific example of themicro-electro-mechanical device described in the foregoing embodimentmodes is described. The micro-electro-mechanical device of the presentinvention can constitute a memory device in which a memory elementincludes a microstructure. In this embodiment mode, an example of amemory device is described in which a peripheral circuit such as adecoder is formed using a semiconductor element or the like, and theinside of a memory cell is formed using a microstructure.

FIG. 16 shows a structure of a memory device 401 which is one example ofthe micro-electro-mechanical device of the present invention.

The memory device 401 includes a memory cell array 402, decoders 403 and404, a selector 405, and a reading/writing circuit 406. A knownstructure can be used for the decoders 403 and 404 and the selector 405.

A memory cell 409 includes, for example, a memory element 408 and aswitching element 407 for controlling the memory element. In the memorydevice 401 described in this embodiment mode, the switching element 407and/or the memory element 408 are/is constituted from a microstructure.

FIGS. 17A and 17B show an example of a structure of the memory cell 409.FIG. 17A is a circuit diagram of the memory cell 409 and FIG. 17B is across-sectional view of the structure.

As shown in FIG. 17A, the memory cell 409 includes the switching element407 constituted from a transistor 410 and the memory element 408constituted from a microstructure.

As shown in FIG. 17B, the memory element 408 includes a space 412 andhas a microstructure formed using the manufacturing method described inforegoing embodiment modes. The memory element 408 is a capacitorincluding conductive layers as structure layers with the space 412interposed. Further, one of the conductive layers is connected to one oftwo high-concentration impurity regions in the transistor 410.

In addition, the space 412 may be closed by being sealed or may beopened. When the space is closed, a reference pressure is sealed thereinand the space can be used as a pressure sensor.

One of the conductive layers is commonly connected to the memoryelements 408 of all the memory cells 409 in the memory device 401. Theconductive layer applies the same potential to all the memory elementsat the time of reading and writing of the memory device, which may bereferred to as a common electrode 411 in this specification.

The memory device having the above structure can be used as a volatilememory, typically as a DRAM (Dynamic Random Access Memory). In themanufacturing process, the memory device can be used as a mask ROM bychanging a gap in a capacitor. The memory device can be used as awrite-once memory by means with which the memory device is broken. Aknown technology can be used for the structure of the peripheral circuitand the driving method or the like.

This embodiment mode can be freely combined with the foregoingembodiment modes.

Embodiment Mode 9

In this embodiment mode, an example of the micro-electro-mechanicaldevice described in the foregoing embodiment modes is described.

The micro-electro-mechanical device of the present invention can beformed as, for example, a fractionation device for separating particularcells. The fractionation device is described hereinafter.

FIGS. 18A and 18B show an example of a basic structure of thefractionation device of this embodiment mode. Here, a fractionationdevice which separates particular cells from two or more cells isdescribed as an example of the fractionation device.

A fractionation device 501 is broadly divided into two parts of anelectric circuit portion 502 and a structure portion 503. The structureportion 503 includes a sensor element 504 and a plurality of gatingmeans 505. The electric circuit portion 502 includes a signal processingmeans 506, a gating control means 507, an information storing means 508,and a communication means 509.

Here, each of the sensor element 504 and the gating means 505 isconstituted from a microstructure with a size corresponding to a cell tobe separated. One sensor element 504 is provided adjacent to one gatingmeans 505, and detects what kind of material exists near the gatingmeans 505. The gating means 505 has a passage which is opened only whena control signal is received from the gating control means 507 andparticular cells exists near the gating means 505, so that theparticular cells pass therethrough.

The signal processing means 506 processes a signal transmitted from thesensor element 504 by amplification, A/D conversion, or the like, totransmit to the gating control means 507. The gating control means 507controls the gating means 505 based on a signal transmitted from thesensor element 504. The information storing device 508 stores a programfile for operating the fractionation device 501, information specific tothe fractionation device 501, or the like. The communication means 509communicates with an external control device 510.

The external control device 510 includes a communication means 511, aninformation processing means 512, a display means 513, an input means514, or the like.

The communication means 511 transmits a signal for controlling thefractionation device 501 and receives information obtained by thefractionation device 501, or supplies driving power to the fractionationdevice 501, or the like. The information processing means 512 performsoperation such as processing information received from the fractionationdevice 501, and processing to transmit information inputted by the inputmeans to the fractionation device 501. The display means 513 displaysinformation obtained by the fractionation device 501, the operationstatus of the fractionation device 501, and the like. The input means514 provides a means of inputting information.

FIG. 18B shows one example of using the fractionation device 501. Thefractionation device 501 having the above structure is disposed betweena mixed cell layer 520 and a specified cell layer 521. The fractionationdevice 501, after receiving information on what cell to be separated orthe like by the external control device 510, detects what kind of cellexists adjacently to the gating means 505 by the sensor element 504.Next, a detection signal is processed by the signal processing means 506and transmitted to the gating control means 507. The gating controlmeans 507 controls the gating means 505 to open the passage only when acell to be separated exists closely to the gating means 505. Further,the gating means 505 passes only the cell to be separated through thepassage in accordance with control by the gating control means 507.

Through the above operation, the fractionation device 501 can separate aparticular cell from mixed cells of two or more kinds. With theforegoing structure, the fractionation device 501 can be controlled toseparate only a cell which fluoresces when irradiated with UV light. Inaddition, a fractionation device having a function of separating onlyparticles which have a minute grain boundary, such as, particlescontaining a radioactive substance, or magnetic ore particles can berealized. Further, the fractionation device 501 is not limited to cellfractionation. For example, using the above structure, the fractionationdevice can also be constituted as a device for separating a particulargas.

The present invention can provide a separation system including thefractionation device 501, the mixed cell layer 520, the specified celllayer 521, and the external control device 510, for separating aparticular cell from mixed cells.

This embodiment mode can be freely combined with the foregoingembodiment modes.

Embodiment Mode 10

In this embodiment mode, an example in which a micro-electro-mechanicaldevice described in the foregoing embodiment modes and wirelesscommunication technique are used.

In recent years, individual-identifying management communicationtechnology using a wireless chip for storing information in anelectronic circuit, a reader/writer for reading and writing informationstored in the wireless chip, and a host system for processing the readinformation and controlling the reader/writer has been used. Thewireless chip used in this embodiment mode is also referred to as awireless communication ID tag, an IC tag, a wireless tag, or variousother names. In this embodiment mode, the wireless chip is referred toas a semiconductor device. The semiconductor device is basically ofnonbattery type which wirelessly communicates with the reader/writer bydriving power obtained through electromagnetic wave emitted from thereader/writer.

FIG. 19A shows an example of this embodiment mode. The semiconductordevice 601 of this embodiment mode includes an antenna 602, amicro-electro-mechanical device 603, and an electric circuit 604. Theelectric circuit 604 includes a wireless communication circuit 605, anda processing circuit 606. The antenna 602 is connected to the wirelesscommunication circuit. The micro-electro-mechanical device 603 isconnected to the processing circuit 606.

The antenna 602 and the wireless communication circuit 605 receive anelectromagnetic wave emitted from the reader/writer 607 which isexternally provided and obtains driving power for driving thesemiconductor device 601. The antenna 602 sends and receives informationto and from the reader/writer 607 through an electromagnetic wave. Theprocessing circuit 606 controls the micro-electro-mechanical device 603based on the information received from the reader/writer 607 orprocesses information which the micro-electro-mechanical device 603 hasreceived from an external object 610, and the like. The processingcircuit 606 can have a so-called feedback mechanism. In the feedbackmechanism, information which has been received from themicro-electro-mechanical device 603 and processed and information whichhas been transmitted from the reader/writer 607 are processed incombination to control the micro-electro-mechanical device 603.

The reader/writer 607 supplies drive power to the semiconductor device601 through an electromagnetic wave and sends and receives informationto and from the semiconductor device 601 through an electromagneticwave. The operation of the reader/writer 607 is controlled by a hostsystem, for example, a computer 608 here. The reader/writer 607 and thecomputer 608 may be connected through a communication line such as a USB(Universal Serial Bus) or may communicate wirelessly through an infraredray or the like.

In addition, as shown in FIG. 19B, the semiconductor device 601 has theantenna 602 and the electric circuit 604. The electric circuit 604 canbe formed by a semiconductor element 631 and a micro-electro-mechanicaldevice 632. The electric circuit 604 has a wireless communicationcircuit, a processing circuit, and the like similarly to FIG. 19A, andthe antenna 602 is connected to a circuit having a wirelesscommunication function in the electric circuit 604. For example, byforming the circuit using the micro-electro-mechanical device 632 withhigh response speed, wireless communication using higher frequency canbe performed.

The semiconductor device 601 of the present invention has the antenna602 and the wireless communication circuit 605 as shown in the drawings,whereby a wire for inputting drive power and a control signal fromoutside is not provided and the semiconductor device is not required tobe connected to the others physically.

FIG. 20 shows a detailed structure of the electric circuit 604 of thesemiconductor device 601. The electric circuit 604 receives anelectromagnetic wave emitted from outside (here, the reader/writer 607)to generate electric power for driving the semiconductor device 601, andcommunicates with outside wirelessly. Therefore, the electric circuit604 has a power source circuit 611, a clock generating circuit 612, amodulating circuit 613, a demodulating circuit 614, a decoding circuit615, an encoding circuit 616, an information judging circuit 617, andthe like, which are necessary for wireless communication. Moreover, insome cases, the semiconductor device has a different structure dependingon frequency or a communication method used for the wirelesscommunication.

Moreover, the electric circuit 604 has functions of controlling themicro-electro-mechanical device 603, processing information from thereader/writer 607, and so on. Therefore, the electric circuit 604 has amemory, a memory controlling circuit, an arithmetic circuit, and thelike. FIG. 20 shows a structure in which the electric circuit 604 has amemory 621, a memory controlling circuit 622, an arithmetic circuit 623,a structure controlling circuit 624, an A/D converting circuit 625, anda signal amplifying circuit 626.

The power source circuit 611 has a diode and a capacitor and can holdconstant voltage by rectifying alternating voltage generated at theantenna 602 and supply the constant voltage to each circuit. The clockgenerating circuit 612 has a filter or a frequency dividing circuit,whereby clock with required frequency can be generated based on thealternating voltage generated at the antenna 602 and the clock can besupplied to each circuit. Here, frequency of the clock generated by theclock generating circuit 612 is basically set to be equal to or lowerthan frequency of an electromagnetic wave with which the reader/writer607 and the semiconductor device 601 communicate each other. Moreover,the clock generating circuit 612 has a ring oscillator and can generatea clock with arbitrary frequency by inputting voltage from the powersource circuit 611.

The demodulating circuit 613 has a filter and an amplifying circuit, sothat a signal included in alternating voltage generated at the antenna602 can be demodulated. The demodulating circuit 613 has a circuithaving a different structure depending on a modulation method used forthe wireless communication. The decoding circuit 615 decodes a signalwhich has been demodulated by the demodulating circuit 613. This decodedsignal is a signal which has been sent from the reader/writer 607. Theinformation judging circuit 617 has a comparing circuit and the like,and can judge whether the decoded signal is a correct signal that hasbeen sent from the reader/writer 607. If the signal is judged to becorrect information, the information judging circuit 617 can send asignal showing that the signal is correct to each circuit such as thememory controlling circuit 622, the arithmetic circuit 623, or themicrostructure controlling circuit 624, and the circuit having receivedthe signal can perform predetermined operation.

The encoding circuit 616 encodes data to be sent from the semiconductordevice 601 to the reader/writer 607. The modulating circuit 614modulates the encoded data and sends the modulated data to thereader/writer 607 through the antenna 602.

The data to be sent to the reader/writer is data unique to thesemiconductor device stored in a memory or data obtained by a functionof the semiconductor device. The data unique to the semiconductor deviceis data such as identification information stored in a nonvolatilememory included in the semiconductor device. The data obtained by afunction of the semiconductor device is, for example, data obtained bythe micro-electro-mechanical device, data to which certain calculationhas been conducted based on the data obtained by themicro-electro-mechanical device, and the like.

The memory 621 can have a volatile memory and a nonvolatile memory andstores data unique to the semiconductor device 601, information obtainedfrom the micro-electro-mechanical device 603, and the like. Although thedrawing shows only one memory 621, it is possible to have a plurality ofmemories in accordance with the kind of information to be stored and afunction of the semiconductor device 601. The memory controlling circuit622 has a function of controlling the memory 621 in the case of readinginformation stored in the memory 621 and writing information in thememory 621. Specifically, the memory controlling circuit 622 cangenerate a writing signal, a reading signal, a memory selecting signal,and the like; specify an address; and the like.

The microstructure controlling circuit 624 can generate a signal forcontrolling the micro-electro-mechanical device 603. For example, in thecase of controlling the micro-electro-mechanical device 603 inaccordance with an instruction from the reader/writer 607, a signal forcontrolling the micro-electro-mechanical device 603 is generated basedon the signal decoded by the decoding circuit 615. In the case wheredata such as a program for controlling operation of themicro-electro-mechanical device 603 is stored in the memory 621, asignal for controlling the micro-electro-mechanical device 603 isgenerated based on the data read from the memory 621. Besides, it ispossible to provide a feedback function for generating a signal forcontrolling the micro-electro-mechanical device 603 based on data in thememory 621, data from the reader/writer 607, and data obtained from themicro-electro-mechanical device 603.

The arithmetic circuit 623 can process data obtained from themicro-electro-mechanical device 603, for example. Moreover, thearithmetic circuit 623 can perform information processing and the likein the case where the microstructure controlling circuit 624 has afeedback function. The A/D converting circuit 625 is a circuit forconverting analog data and digital data and transmits a control signalto the micro-electro-mechanical device 603. Alternatively, the A/Dconverting circuit 625 can convert data from themicro-electro-mechanical device 603 and transmit the data to eachcircuit. The signal amplifying circuit 626 can amplify a weak signalobtained from the micro-electro-mechanical device 603 and transmits theamplified signal to the A/D converting circuit 625.

The electric circuit 604 can have the foregoing circuit or the like.Although the electric circuit has the wireless communication circuit 605and the processing circuit 606 in FIG. 19A, it is difficult to clearlydiscriminate, in some cases, where the wireless communication circuit605 ends and where the processing circuit 606 starts in a detailedcircuit shown in FIG. 20. This is because, for example, the memory 621can be provided for either the wireless communication circuit 605 or theprocessing circuit 606. More specifically, the electric circuit 604 canhave a nonvolatile and non-rewritable memory for storing informationunique to the semiconductor device and a nonvolatile and rewritablememory for storing data which controls the micro-electro-mechanicaldevice and data which is obtained from the micro-electro-mechanicaldevice. The nonvolatile and non-rewritable memory can be provided as thewireless communication circuit 605 and the nonvolatile and rewritablememory can be provided as the processing circuit 606.

Therefore, the electric circuit 604 has the wireless communicationcircuit 605 for performing wireless communication and the processingcircuit 606 for controlling the micro-electro-mechanical device 603 andprocessing an instruction from the reader/writer 607. As specificcircuits for achieving those functions, the power source circuit 611,the memory 621, and the like described with reference to FIG. 20 aregiven. Whether these circuits form the wireless communication circuit605 or the processing circuit 606 changes in accordance with thefunction and the like of the semiconductor device 601.

Although Embodiment Mode 1 is applied for the micro-electro-mechanicaldevice 603 in this embodiment mode, this embodiment mode can be freelycombined with the foregoing embodiment modes.

An antenna 650 is formed in a step of forming the conductive layer 117in Embodiment Mode 1 (FIG. 21A).

In addition, as shown in FIG. 21B, an antenna 651 can be formed outsidethe second sheet member 125. In that case, a wire 652 which electricallyconnects with the antenna 651 is formed in advance. Thus, asemiconductor device utilizing wireless communication can bemanufactured. In addition, a structure in which driving voltage of thesemiconductor device is obtained can be realized by forming a powergeneration element using a piezoelectric material and thermoelectricmaterial at the same time of forming the micro-electro-mechanical deviceforming portion. In that case, a structure may be employed in which asemiconductor device has both the foregoing power generation element andthe antenna 651 and power is stably supplied. In addition, a structurewhich serves as a capacitor (a capacitor or battery) can be formed bychanging a thin-film material or the structure thereof in themicrostructure included in the micro-electro-mechanical device. Then,the power obtained by the foregoing power generation element and antennacan be stored in the capacitor, thereby supplying power to thesemiconductor device. In addition, constant supply of the power canprovide a longer wireless communication distance and usable time of thesemiconductor device.

Embodiment Mode 11

In this embodiment mode, a specific structure and application example ofthe semiconductor device described in the foregoing embodiment mode aredescribed with reference to the drawings.

Here, an example of the semiconductor device having a function ofsending an operation signal of the micro-electro-mechanical device,discharging medicine to an area affected by disease, mixing dangerouschemicals, or the like is described.

FIG. 22 is an example of the structure of a micro-electro-mechanicaldevice 700 in this embodiment mode. The micro-electro-mechanical device700 has a tank 701 for storing medicine, chemicals, or the like and adischarge opening 702 for discharging medicine, chemicals, or the like.In addition, the antenna 650 is formed to communicate with thereader/writer wirelessly.

The tank 701 can be referred to as a space by being opened.

The micro-electro-mechanical device 700 receives driving power throughan electromagnetic wave emitted from the reader/writer which isexternally provided, and communicates wirelessly with the reader/writer.Then, the micro-electro-mechanical device 700 receives an operationsignal from the reader/writer. The micro-electro-mechanical device 700receives different polarities between the first structure layer and thesecond structure layer of the microstructure. The first structure layeris attracted to the second structure layer and is bent due toelectrostatic force. Thus, the micro-electro-mechanical device 700operates so that the tank 701 discharges the medicine or chemicals 703therein through the discharge opening 702 (FIG. 23).

A semicondutor device 704 shown in FIG. 24A has a capsule 705 coatedwith a protective layer, in which the micro-electro-mechanical device700 of this embodiment mode is provided. A passage 706 from thedischarge opening 702 of the micro-electro-mechanical device 700 isprovided. The passage 706 is not necessarily provided and the medicineor chemicals may be discharged outside the capsule 705 directly from thedischarge opening 702. A filler 707 may be filled between the capsule705 and the micro-electro-mechanical device 700.

The protective layer formed over the surface of the capsule preferablycontains diamond like carbon (DLC), silicon nitride, silicon oxide,silicon nitride oxide, or carbon nitride. A known capsule and filler canbe appropriately used. By providing the protective layer for capsule,the capsule and the semiconductor device can be prevented from beingmelted or changed in property inside of a body.

Besides, by making the outer surface of the capsule have a curved shape,the capsule does not hurt a human body; therefore, the capsule can beused safely.

The semiconductor device 704 of this embodiment mode can be put into ahuman body and injects a medicine to an area affected by disease. Inaddition, when the semiconductor device 704 is provided with additionalfunction such as a sensor for detecting biological function data of bodyby measuring a physical amount and a chemical amount or a sampling meansfor sampling cells in the affected area, the obtained information can besignal-converted and processed by the electrical circuit and be sent tothe reader/writer by wireless communication. Depending on the structureof the electrical circuit in the semiconductor device, the semiconductordevice can have an advanced function, such as a function of exploringthe area affected by disease based on the information obtained by themicro-electro-mechanical device, a function of judging whether themedicine is injected or not, or the like.

As shown in FIG. 24B, an examinee 708 swallows the semiconductor device704, and the semiconductor device 704 is moved to a predeterminedposition in which the medicine is injected through a body cavity 709.The reader/writer 710 controls the semiconductor device 704 throughwireless communication and the semiconductor device 704 discharges themedicine.

The semiconductor device 704 of this embodiment mode is applied not onlyto a medical purpose, but to wide application as a remote-controlleddischarge device. For example, mixture of chemicals with a worker atrisk such as generation of harmful gas or possibility of explosion canbe performed by remote-controlling the semiconductor device 704 of thisembodiment mode with the tank 701 thereof filled with the chemicals.Thus, a risk for the worker can be lowered significantly.

Embodiment Mode 12

As a specific example and another application example of thesemiconductor device described in the foregoing embodiment modes aredescribed in this embodiment mode with reference to the drawings.

Here, an example of a semiconductor device in which amicro-electro-mechanical device is used as a pressure sensor isdescribed.

As shown in FIG. 25A, a micro-electro-mechanical device 801 includes asensor element 804 having a first conductive layer 802 and a secondconductive layer 803. In addition, the micro-electro-mechanical device801 has a space 816 with which the first conductive layer 802 can movedue to electrostatic force, pressure, or the like. That is, the sensorelement 804 is a variable capacitor in which the distance between thefirst conductive layer and the second conductive layer changes whichmeans the space changes in shape.

In addition, the space 816 may be closed by being sealed or may beopened. When the space is closed, a reference pressure is sealed thereinand the space can be used as a pressure sensor.

Utilizing this structure, the sensor element 804 can be used as apressure sensor element in which the first conductive layer 802 is movedby pressure.

The micro-electro-mechanical device 801 has an antenna 805 forcommunicating with a reader/writer wirelessly. Themicro-electro-mechanical device wirelessly communicates with thereader/writer by driving power obtained through electromagnetic waveemitted from the reader/writer.

FIG. 25B is a specific example of the micro-electro-mechanical device801 used as a pressure sensor. When the inflation pressure in a tire 806of a car is lowered, the tire 806 deforms significantly and theresistance increases, which lead to deterioration in mileage performanceand accidents. The semiconductor device of this embodiment mode canprovide a system for monitoring the inflation pressure of the tire 806relatively easily and regularly.

As shown in FIG. 25B, the semiconductor device 807 in which themicro-electro-mechanical device 801 coated with a protective layer isplaced at a wheel portion 808. A plurality of the semiconductor devices807 is preferably provided. In that case, the semiconductor devices areplaced so that the gaps therebetween are the same.

Then, a reader/writer 809 is placed close to the semiconductor device807 and performs wireless communication, thereby obtaining informationon the inflation pressure of the tire 806. The reader/writer 809 may bemounted on a vehicle. The wireless communication technique or the likeare similar to that of foregoing Embodiment Mode 10.

According to this embodiment mode, an inflation pressure of tire can bemonitored relatively easily and regularly without going to a carmaintenance shop such as a gas station. When the reader/writer ismounted on the vehicle, the inflation pressure of the tire is monitoredconstantly, thereby preventing blowing out of the tire. This applicationis based on Japanese Patent Application serial no. 2005-258072 filed inJapan Patent Office on Jun. 9, in 2005, the entire contents of which arehereby incorporated by reference.

1. A manufacturing method of a micro-electro-mechanical device,comprising: providing a first structure layer in a first region over atop surface of a flexible substrate, the flexible substrate including afirst opening in the first region; providing a second structure layer ina second region over the top surface of the flexible substrate, theflexible substrate including a second opening in the second region; andforming a space, comprising the first opening and the second opening, bybending the flexible substrate so as to put into contact a first area ofa bottom surface of the flexible substrate with a second area of thebottom surface of the flexible substrate so that the first opening andthe second opening face each other and the first opening is incommunication with the second opening.
 2. The manufacturing method of amicro-electro-mechanical device, according to claim 1, wherein the firststructure layer, the second structure layer, and the space form acapacity.
 3. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 1, wherein the first structure layer containssilicon.
 4. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 1, wherein the second structure layerincludes at least one element selected from the group consisting ofaluminum, titanium, molybdenum, tungsten, and silicon.
 5. Themanufacturing method of a micro-electro-mechanical device, according toclaim 1, wherein the space is closed so as to be used as a pressuresensor.
 6. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 1, wherein the space is opened so as to beused as a discharge device.
 7. The manufacturing method of amicro-electro-mechanical device, according to claim 1, wherein a step ofbending the flexible substrate is performed with reference to a mark foralignment or a groove.
 8. A manufacturing method of amicro-electro-mechanical device, comprising: forming a peeling layerover a first substrate; forming a first structure layer in a firstregion over the peeling layer; forming a first insulating layer coveringthe first structure layer; forming a second structure layer over thefirst insulating layer in a second region; forming a second insulatinglayer so as to cover the first insulating layer and the second structurelayer; removing the peeling layer and separating the first substrate;transferring at least the first structure layer and the second structurelayer to a top surface of a second substrate having flexibility providedwith a first opening and a second opening; and forming a space,comprising the first opening and the second opening, by folding thesecond substrate so as to put into contact a first area of a bottomsurface of the second substrate with a second area of the bottom surfaceof the second substrate so that the first opening and the second openingface each other.
 9. The manufacturing method of amicro-electro-mechanical device, according to claim 8, wherein the firststructure layer, the second structure layer, and the space form acapacity.
 10. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 8, wherein the second insulating layercontains an organic material.
 11. The manufacturing method of amicro-electro-mechanical device, according to claim 10, wherein theorganic material includes an epoxy resin.
 12. The manufacturing methodof a micro-electro-mechanical device, according to claim 8, wherein thefirst structure layer contains silicon.
 13. The manufacturing method ofa micro-electro-mechanical device, according to claim 8, wherein thesecond structure layer includes at least one element selected from thegroup consisting of aluminum, titanium, molybdenum, tungsten, andsilicon.
 14. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 8, wherein the peeling layer includes atleast one element selected from the group consisting of tungsten,molybdenum, titanium, tantalum, niobium, nickel, cobalt, zirconium,zinc, ruthenium, rhodium, palladium, osmium, and iridium.
 15. Themanufacturing method of a micro-electro-mechanical device, according toclaim 8, wherein the peeling layer is removed by an etchant comprising agas or a liquid containing halogen fluoride or a halogen compound. 16.The manufacturing method of a micro-electro-mechanical device, accordingto claim 8, wherein the space is closed so as to be used as a pressuresensor.
 17. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 8, wherein the space is opened so as to beused as a discharge device.
 18. The manufacturing method of amicro-electro-mechanical device, according to claim 8, wherein a step offolding the second substrate is performed with reference to a mark foralignment or a groove.
 19. The manufacturing method of amicro-electro-mechanical device, according to claim 8, wherein the firstopening and the second opening are provided in a position correspondingto the first structure layer and the second structure layer,respectively.
 20. A manufacturing method of a micro-electro-mechanicaldevice, comprising: forming a peeling layer over a first substrate;forming a first structure layer in a first region over the peeling layerand forming a semiconductor layer in a second region over the peelinglayer; forming a first insulating layer covering the first structurelayer and the semiconductor layer; forming a first opening in the firstinsulating layer in the second region; forming a conductive layer so asto fill the first opening and forming a second structure layer in thesecond region; forming a second insulating layer so as to cover thefirst insulating layer, the conductive layer, and the second structurelayer; removing the peeling layer and separating the first substrate;transferring at least the first structure layer and the second structurelayer to a top surface of a second substrate having flexibility providedwith a second opening and a third opening; and forming a space,comprising the first opening and the second opening, by folding thesecond substrate so as to put into contact a first area of a bottomsurface of the second substrate with a second area of the bottom surfaceof the second substrate so that the second opening and the third openingface each other.
 21. The manufacturing method of amicro-electro-mechanical device, according to claim 20, wherein thefirst structure layer, the second structure layer, and the space form acapacity.
 22. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 20, wherein the second insulating layercontains an organic material.
 23. The manufacturing method of amicro-electro-mechanical device, according to claim 22, wherein theorganic material includes an epoxy resin.
 24. The manufacturing methodof a micro-electro-mechanical device, according to claim 20, wherein thefirst structure layer contains silicon.
 25. The manufacturing method ofa micro-electro-mechanical device, according to claim 20, wherein thesecond structure layer includes at least one element selected from thegroup consisting of aluminum, titanium, molybdenum, tungsten, andsilicon.
 26. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 20, wherein the peeling layer includes atleast one element selected from the group consisting of tungsten,molybdenum, titanium, tantalum, niobium, nickel, cobalt, zirconium,zinc, ruthenium, rhodium, palladium, osmium, and iridium.
 27. Themanufacturing method of a micro-electro-mechanical device, according toclaim 20, wherein the peeling layer is removed by an etchant comprisinga gas or a liquid containing halogen fluoride or a halogen compound. 28.The manufacturing method of a micro-electro-mechanical device, accordingto claim 20, wherein the space is closed so as to be used as a pressuresensor.
 29. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 20, wherein the space is opened so as to beused as a discharge device.
 30. The manufacturing method of amicro-electro-mechanical device, according to claim 20, wherein thesemiconductor layer is an active layer in a semiconductor elementincluding a channel formation region, a source region, and a drainregion.
 31. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 20, wherein the conductive layer acts as anantenna.
 32. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 20, wherein a step of folding the secondsubstrate is performed with reference to a mark for alignment or agroove.
 33. The manufacturing method of a micro-electro-mechanicaldevice, according to claim 20, wherein the second opening and the thirdopening are provided in a position corresponding to the first structurelayer and the second structure layer, respectively.